He was talking about 512 "processors" (or CPUs) in a single computer running one operating system, not 512 computers. Linux only supports 64 CPUs (although I read where it was hacked to support 128 and successfully run on more than 64 but not at optimal performance), but Windows I believe only currently supports 8 CPUs. Windows only runs on Intel boxes and I don't believe there is an Intel based machine out there with more than 8 CPUs. You have to look to Sun, IBM, etc with non-Intel processors to find computers with that many.
Now the largest supercomputers are made up of many "computers" with 2 to many processors each using special hardware/cabling and clustering software. The largest supercomputers have over 10,000 processors linked together to form a single logical machine.
And on normal simple symetric multi-processor (SMP) boxes the application would have to be multithreaded to take advantage of having more than one CPU. If the application is not multithreaded then the application will only bind and run on one of the multiple CPUs. I'm not sure, but I would guess that Q3 and most of the other games are single threaded, could be wrong.
And it is the video card that is the biggest influencing factor on frame rates (assuming you have at least a fast enough processor to keep up with the underlying tasks and enough memory so that the game can speedily shovel video data to the video card).
SETI just breaks up the data to be processed into many small chunks and runs the same program on many computers for the intense processing of the small manageable chunks of data, putting the results back together on a single computer system back at Berkeley. This is sort of like multithreading but it is multithreading across many computers, not just many CPUs on a single computer.
[ July 29, 2002: Message edited by: VoidMain ]